org.apache.sling.launchpad.base.shared
Class LauncherClassLoader

java.lang.Object
  java.lang.ClassLoader
      java.security.SecureClassLoader
          java.net.URLClassLoader
              org.apache.sling.launchpad.base.shared.LauncherClassLoader

public class LauncherClassLoader
extends java.net.URLClassLoader

The LauncherClassLoader extends the standard Java VM URLClassLoader such, that classes and resources which are contained in the launcher JAR File are never looked up in the parent class loader.

This class loader shields the Sling OSGi framework completely from the environment because

• Classes and resources contained in packages provided by the launcher JAR file are only looked up in the launcher JAR file
• Classes and resources from the environment are only used from within the framework if the framework is configured to do so by the org.osgi.framework.bootdelegation or org.osgi.framework.systempackages framework properties.

The first point is important if Sling is deployed into any container, which provides some or all of the same packages as the Sling launcher JAR file. One such example is the Glassfish v3 Prelude application service, which itself runs in a Felix OSGi framework and sort of leaks the classes into the web application.

In the general case, we cannot prevent any leaking of classes, which may also be the OSGi core or compendium libraries, into Sling. So, this class loader is the barrier for this leaking and shields Sling from the environment unless explicitly configured to use this leaking.

Instances of this class loader are setup with the launcher JAR file as the only contents of the URLClassLoaders class path and the class loader of this class itself as the parent class loader.

Method Summary

java.net.URL	getResource(java.lang.String name) Return an URL to the requested resource.
protected java.lang.Class<?>	loadClass(java.lang.String name, boolean resolve) Load the name class and optionally resolve it, if found.

Methods inherited from class java.net.URLClassLoader

addURL, definePackage, findClass, findResource, findResources, getPermissions, getURLs, newInstance, newInstance

Methods inherited from class java.security.SecureClassLoader

defineClass, defineClass

Methods inherited from class java.lang.ClassLoader

clearAssertionStatus, defineClass, defineClass, defineClass, defineClass, definePackage, findLibrary, findLoadedClass, findSystemClass, getPackage, getPackages, getParent, getResourceAsStream, getResources, getSystemClassLoader, getSystemResource, getSystemResourceAsStream, getSystemResources, loadClass, resolveClass, setClassAssertionStatus, setDefaultAssertionStatus, setPackageAssertionStatus, setSigners

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

loadClass

protected java.lang.Class<?> loadClass(java.lang.String name,
                                       boolean resolve)
                                throws java.lang.ClassNotFoundException

Load the name class and optionally resolve it, if found.

This method checks whether the package of the class is contained in the launcher JAR file. If so, the launcher JAR file is looked up for the class and class loading fails if not found. Otherwise the standard class loading strategy is applied by calling the base class implementation.

Overrides:

loadClass in class java.lang.ClassLoader

Throws:

java.lang.ClassNotFoundException

getResource

public java.net.URL getResource(java.lang.String name)

Return an URL to the requested resource.

This method checks whether the package of the resource is contained in the launcher JAR file. If so, the launcher JAR file is looked up for the resource and resource access fails if not found. Otherwise the standard resource access strategy is applied by calling the base class implementation.

Overrides:

getResource in class java.lang.ClassLoader